Update the plugin site with a simple "How To Use" section.

In order analyse a PHP project with Sonar, it is still required to a add a simple POM file into the project root.
For PHP developers with no Maven experience it may be difficult to understand where to start. (Actually currently it's not really mentioned at all at the plugin site)

It would be good to include a simple "How To Use It" like the following:

How To Use It:

• Make sure Apache Maven 2.2.1 is installed on the machine hosting the PHP project (see http://maven.apache.org/).
• Create a POM file (pom.xml) inside the root directory of your project identifying your project within Sonar:

  <?xml version="1.0" encoding="UTF-8"?>
  <project xmlns="http://maven.apache.org/POM/4.0.0" 
           xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
           xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 
               http://maven.apache.org/xsd/maven-4.0.0.xsd">
  
    <modelVersion>4.0.0</modelVersion>
  
    <groupId>com.mycompany.projectGroupId</groupId>
    <artifactId>projectName</artifactId>
    <name>Human Readable Project Name</name>
    <version>1.0-SNAPSHOT</version>
  
    <description>
      Some more details on "Project Name"
    </description>
  
    <build>
      <outputDirectory>target</outputDirectory>
      <sourceDirectory>sources</sourceDirectory>
      <testSourceDirectory>tests</testSourceDirectory>
    </build>
  
    <properties>
      <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
      <sonar.language>php</sonar.language>
    </properties>
  </project>
    

• Execute "mvn sonar:sonar" in the same path to analyse your project.